


Possession

by orphan_account



Category: Undertale (Video Game)
Genre: F/F, F/M, Flowey Is A Dick, Flowey is an emotional wreck, Frisk's Pronouns are They/Them, Nonbinary Frisk, PTA Sans, PTSD Sans, Post-Traumatic Stress Disorder - PTSD, Sans Has Issues, Sans Has Night Terrors, Sans Makes Puns, Sans Needs A Hug, Selectively Mute Frisk, don't get me started on sans, flowey possession au, goddammit Linda, hes gonna suffer, idk what to call that, just read it please, oh did I mention Sans needs a fucking hug, oops forgot to add that one sorry, oops too many tags
Language: English
Status: In-Progress
Published: 2016-04-01
Updated: 2016-05-06
Packaged: 2018-05-30 05:48:30
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 4
Words: 3,184
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6411292
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>(really lame title wow)<br/>(I'm bad at summaries too)<br/>(ON HIATUS, MAY OR MAY NOT FINISH)<br/>A year after the barrier fell. Frisk is now ten, and they are slowly starting to fit in, just like the monsters. Of course, some people don't like it, and frankly, some monsters don't either. Some stay underground.<br/>Toriel has become headmaster for a multi species school, to many of the human parent's dismay. Sans finds himself being dragged into his wife's school, volunteering to join the PTA meetings for Frisk's grade. Dealing with the pressure of some idiotic parents, Sans tries to get away by volunteering for a trip to the Underground. However, Frisk has other plans, and sneaks home that soulless flower demon.<br/>Sans can't stop the flashbacks, hallucinations, nightmares, or the boiling hatred inside- just how long can he keep it at bay for Frisk's sake?</p>
            </blockquote>





	1. PTA Dunkle

**Author's Note:**

> Warning for ENTIRE FIC:  
> Strong language + violence  
> Will put warnings in the notes when major amounts take place.

 

 

   Sans walked into the courtyard to pick up Frisk. Toriel was working late, so he had offered to take them home. Why not?

Waving, Frisk ran over to him, their hands moving in a blur. ' _Dunkle Sans! Can we go over to Alphys and Undyne's place? Papyrus texted me. He's there too.'_

"sure, why not, kiddo? text tori for me, would'ja? thanks." Sans responding, following them outside to the gates. 

' _Did you walk?'_

"nah, shortcutted." He winked. "why? you wanna walk?" 

' _No! I like the shortcuts.'_ Frisk giggled, their phone ringing. 

"Hello, my child! This is Toriel. Sans seems to have left his phone at home, hence him not answering. From the text, I suppose he has picked you up already?" Toriel's soft voice came over the phone. Frisk handed the phone to Sans, who took it with a sheepish glance sideways.

"hey tori. its okay we hang at alphys and undyne's place, right?"

"Yes, of course! Shall I stop by Muffet's Bakery to bring something over after my meeting?" 

"sure, that'd be nice. everyone  **bread** -der appreciate it." He said with a chuckle, earning a giggle from Frisk.

"Haha! Alright! I'll see you all at six. Be good, my dears." 

Frisk took their phone but and sent a quick text to Papyrus.  _On our way._ Sans grin widened as they walked out of the school's pickup area, the kid's playing eventually fading. It was a beautiful day. Kids are laughing, friends are waiting. On days like these, kids like Frisk, should be having a good time. But women like that one, who was glaring at them with loathing and judgement, should be _kindly minding their own business._

 

* * *

 

 

"HUMAN! BROTHER! YOU HAVE ARRIVED!" 

"Heya punks! We were almost gonna start the movie without ya!" Undyne yelled, rather dramatically.

"H-hey guys! And no, we would've waited for you!" Alphys said, more directed towards Undyne. 

"I SHALL PREPARE THE PASTA!" 

"wait a second, pap. tori's gonna bring over some of muffet's bakery stuff. besides, its only two-thirty."

' _What movie are we watching?'_

"Well, it's either Jaws or Jurassic World!" Undyne said. "BUT WHO CARES BOTH ARE REALLY VIOLENT, RIGHT AL?!" 

"UNDYNE! WE SHOULD PICK THE  _LEAST_ VIOLENT ONE TO WATCH!" Papyrus protested. 

"U-uh, well, Jurassic World has really g-great graphics, and it's longer with a better storyline and-"

"I didn't know you were a nerd about movies, too!" Undyne laughed, swooping the lizard off her feet and plopping her down onto the large couch. Undyne snuggled up next to her very small, flustered wife. 

Frisk sat next to them, giggling and giving Alphys a reassuring thumbs up. Papyrus sat down next to them, followed by Sans leaning on the arm of the couch. The theme started to play, and Undyne threw a spear at the light switch. Alphys was grateful the whole freaking house didn't lose power. 

 

Sans soon dozed off, much to Papyrus' annoyance. It was now six o' five. There was a knock at the door. 

 

"It is Toriel! Sorry for arriving late. I have baked treats!" Tori's soft voice came through the door.

Sans sprung up to open it, to his instant embarrassment. Walking a bit slower to the door, he opened it and said, "hey tori. its fine.  **rye** so serious?" 

Papyrus groaned, while a soft chuckle echoed from Toriel in the doorway. 

"YOUR MAJESTY- I MEAN MISS TORIEL- I APOLOGIZE FOR MY BROTHERS HUMOR." 

"nah, i think I'm pretty  **humerus.** " Sans grinned. Another groan from everyone.

"Don't worry, Papyrus. I  **loaf** him to death!" Toriel laughed. Sans snorted, a blue blush forming on his cheeks. Today was nice.

 

* * *

 

 

   Eight o clock. Frisk was up in bed. They finished their homework rather early with Sans helping them. Papyrus offered to read them a bed-time story in his room, but of course, as usual, they fell asleep again. With a chuckle, Sans tucked them both in. " ~~You used to fall asleep reading to him like that."~~ A voice said. 

"yeah." Sans smile turned to a sad one. "im working on a way to bring you back. i still am. i promise."

 _"_ ~~You hate making promises, Sans."~~

"well, frisk promised this was the last reset. so, i made a promise so myself. and to you, dad. i didn't forget."

~~"The void's power is dimming again."~~

"heh, okay. see you soon, gasty." 

 ~~"Sans you know I hate that~~ ~~nickna-"~~  Gaster's voice was cut off as the connection severed.

"i know." 

"Sans? Who are you talking to? May I come in?" Toriel asks through her side of the door. 

"sure. you know that door is always open." Sans responded. "and as to who i was talking to, uh, just thinking out loud." 

Toriel scooped him up like he weighed nothing- which was probably true. He was just a skeleton in a hoodie. 

"I wanted to ask you if you could participate in the PTA meetings for Frisk. I can not because I am the headmaster. Or principal. Human words have changed over the time we were underground." 

"sure. what could go wrong?"

 

* * *

 

((AN: little bit of language warning, Linda being an ass and discriminating monsters.))

 

  Sans was running late, and walking would make him ten minutes late. Sighing, he gathered his magic and teleported straight into the cafeteria. A woman gasped loudly and rather dramatically. "What the-?! Oh, a skeleton monster. Sweetie, where's your, uh, parents?" 

 _in the fucking void, wiseass._ "sorry. im actually a parent, here. im sans, sans the skeleton. im here for the pta meeting because  _frisk is my child._ " He said with a blank expression, his white pupils fading. 

"Oh! Toriel called me about you. I'm Steve. Welcome to the PTA, Sans!" Steve said, more friendly. "We're about to start."

 

* * *

 

 

"There has been a suggestion about the history of monsters as a criteria. I propose we completely shut down this idea because it is utterly useless and quite disturbing-"

"woah woah woah." Sans called out from the back table, his feet propped up against the bench. "linda, is it? i gotta say, you're doing a pretty good job of being a total idiot." All the other parents looked shocked. No one has  _ever_ stood up to Linda. "as i was saying," Sans continued, cutting her off. "what do you know about monster history? in fact, monsters are quite smart, believe it or not. one of our royal scientists built a machine that saved the entire race by harvesting the heat from a certain section under the mountain. the CORE, as it was called, harnessed geothermal energy to a much greater efficiency than your technology. additionally, i personally took part in the human DETERMINATION and SOUL study. humans will also be given the chance to learn about the war that you guys thought was  _okay_ to just forget about. it also gives them a chance to learn more about their magical essence, as well as us monsters. possibly ending the  _hatred and discrimination_ in both species."

Gawking, Linda clearing her throat. "Who will teach?! No human ever will! Many parents are already uncomfortable as it is with a monster gym teacher and assistant, along with a principal!"

"i can." Sans said with a shrug. 

Linda's jaw dropped. "Oh really? Because from what I've gathered today at this meeting is that you are lazy and-" 

"woah, hold on there. i may be lazy, yeah. not gonna deny that. but, what you don't know is," Sans paused to savor the look of distaste on Linda's face. "i've been working at that lab not too far from here, with my friend, the formal royal scientist. and, now officially, three of my four phd's are recognized by the government. The last one is in entirely magic related business, so i don't really care about it not being recognized. i've also done a major scientific study of space time anomalies, the space called the void, human soul anatomy and properties, and shall i continue, or is that enough evidence for you?"  

 

 

* * *

 

 


	2. Feild Trip

**Summary for the Chapter:**

> After a long night of work, Sans realizes he had offered to chaperone the feild trip back to the underground for Frisk's class. Things don't go well, especially with Linda coming along.

**Notes for the Chapter:**

> Please comment feedback! Taking critisim c:

Whirring filled Sans' room. The small orb hummed on his desk, giving off a small glow. "gaster? is it working?"  
" ~~Yes- You did it, Sans!~~ " A form materialized in the center of his room.  
"haha! yes. finally, closer." A grin formed on his tired face. Gaster noted the dark circles under Sans eye sockets.  
" ~~How long have you been working on this?~~ "  
"mostly when everyone's asleep." He said with a shrug.  
" ~~On top of PTA meetings and work at the human's lab with Alphys?~~ " Gaster inquired. Sans finally got what was going on.  
"don't worry, i'm fine. i can do it." He said quickly, staring at the calculations on his desk. He felt a presence near his right side.  
" ~~Try changing the 3rd number to a two.~~ "  
Sans tinkered with the device, swapping a few digits with a bony finger. He felt a hand on his shoulder.  
"i-it worked,"  
" ~~You did it.~~ " His voice was clearer, less fuzzy.  
"i'm so close." He whispered. "i'll get you back." Standing up, he hugged Gaster, his form feeling solid and less.. wrong. "dad. i'm going to do it. even if i have to go all the way back underground. i will bring you back." Sans said shakily. "i never forget."  
" ~~Well, then.~~ " Gaster said. " ~~Better get started, lazybones.~~ " His father said with a chuckle. " ~~That device is really draining it's power. I'll see you soon.~~ " Sans flashed a grin.  
"see ya, gasty."  
" ~~Sans! What did I~~ -"  
click.  
A very not amused form of Gaster slowly faded. Sans laughed. The rapidly fading figure moved his bony hands.  
'get some rest first, sansy.'  
Now it was Sans turn to be unamused. "fine."  
With a sigh, he pushed the papers and blueprints into a drawer and climbed into bed. 2:27 am. Oh shit. The field trip back to the underground was tomorrow. Good thing Tori was coming too, or else he'd lose his shit with Linda. And her stupid kid, too.

* * *

"alrighty, kids. today we're gonna be visiting the underground. now, i'm not gonna bore ya with history, save that for my next semester classes," He winked. "anyway, follow me. frisk, you wanna explain?" 

' _This is where I first fell into the underground. This hole, right at the base of Mount Ebott.'_

Monster Kid translated for the class. 

"Yes, my children. Now, I realize it is a long drop down. Worry not! Sans and I have devised a plan to get you all down safely!" Toriel said, standing at the base of the hole. 

"Nothing about this is safe." Linda growled.

Sans summoned his gaster blasters. All the children 'oohh'ed and 'ahhh'ed. Frisk walked up to one. They pet the skull like a dog, and Sans ordered it to hover lower. "now everyone climb on." 

"That is utterly crazy!" Linda yelled. 

"well, there is another option." Sans shrugged, his bony hands moving in a blur to suggest something privately to Frisk. They nodded, and with a grin, they jumped down. Linda screamed. 

Sans laughed, teleporting, catching Frisk in midair halfway down the chasm. The two smiled at each other, before reappearing next to Toriel and in front of the class and Linda. 

"well, thats the other option. but, to warn you, i may be a little bit slow with your son." He winked. 

 

* * *

"These are the ruins. Previously, I was the caretaker of the ruins and all the monsters here. I also cared for any humans that fell down." Toriel explained, leading the class through the golden flowers. "All these puzzles are already solved, so everyone follow me!" 

"This place is in shambles. An utter mess." Linda complained. 

"tori, how 'bout i lead the class?" Sans spoke up, walking away from Linda. He was not in the mood for her shit. "hey where's frisk?" They hurried after the class, a nervous grin plastered on their face. 

"Please, no one wander off." Toriel addressed the class. "The ruins are a place to get lost in." 

' _Trust me, I know!'_ Frisk signed. MK laughed, and so did the class, Frisk giggling along with them. 

As the group came upon the door, Sans whispered something to Toriel, before vanishing. The kids stared, wide eyed. 

"Where did he-" Linda began angriliy, to be cut off by a muffled voice from the other side. 

"knock knock." 

"Who's there?" The class chorused. 

"dishes."

"Dishes who?" Toriel giggled. 

"dishes a very bad joke." 

The entire class laughed while Linda scowled. Toriel opened the door, greeted by Sans at the other side, snow lightly falling around them. 

"hiya class. im sans.  ~~~~ **ice** to meet ya. oh wait, you already  ** ~~~~snow** me." 

All the kids laughed, running out to play in the rapidly falling snow. "How is there snow under a mountain?! We should've brought coats!" Linda complained.

"oh come on linda.  **chill out.** " 

"Alright children, let's get a move on. We only have until two." 

 

 

* * *

 

 "And that concludes our epic tour of the underground, children! I hope you all enjoyed yourselves." 

"Great great, it's over. Now, how do we get back to school?" Linda called out rudely from the back of the class. 

"oh, right. uh, i hired ol' fluffybuns to pick us up. hope its okay." 

"No, it's alright." Toriel said. "We have been. making.. progress. Anyway, children, time to head home!" 

Sans swore he couldv'e saw Frisk's backpack twitch. 

* * *

 

 

"that went well, didnt it?" Sans asked, laying in his usual spot in the couch. Papyrus grumbled something about Sans hogging the couch. 

"relax bro. you, undyne and al still have enough room." Sans said with a shrug. 

"I believe the children enjoyed themselves." Toriel said. "Although, Linda didn't seem pleased." She admitted. Frisk tugged on her sleeve. She turned to face them. "Oh, my child, what is it? What do you have behind your back?" Toriel asks softly. 

Frisk revealed a brown pot, with a dreadfully familiar shape inside. Sans eye flared cyan. Flowey looked up and met his eyes with a cruel snicker. "Ohh look~ smiley trashbag looks unhappy to see me~" 


	3. haha

**Summary for the Chapter:**

> He came back to reality, Papyrus and Undyne pinning him down against the couch. He saw Toriel and Alphys trying rapidly to free a terrified Frisk and an annoyed Flowey before the whole world went dark.

**Notes for the Chapter:**

> ask and you shall recieve

Sans could only allow his magic to build as he faced the demon that was the cause of half his nightmares. He stood up, blue magic building within his soul. The whole room went dark. He couldn't hear the voices of his friends calling for him to stop. Frisk's soft, brown eyes turned to Chara's demonic, red ones. Flowey's innocent face turned evil, a sickly grin growing on his face. "no. get the fuck outta here," Sans yelled, struggling against the vines that constricted around him. Reaching out with anger and terror, he turned Chara's soul blue, flinging them across the room, along with Flowey. He made layers of bones form, trapping the two. The vines grew tighter. "nonono!" Sans thrashed, trying to get away. He came back to reality, Papyrus and Undyne pinning him down against the couch. He saw Toriel and Alphys trying rapidly to free a terrified Frisk and an annoyed Flowey before the whole world went dark.

  
" _Hohoho!~ You're so powerful, Papyrus~" Flowey cooed._  
_"WHY THANK YOU. I, THE GREAT PAPYRUS, AM EXTREMELY GREAT! NYEH!"_  
_"I know a way us both can be even greater~" Flowey said with a smile. Vines wrapped around Papyrus' wrists._  
_"UH, MAYBE SOME OTHER TIME?"_  
_"Who ever said you had a choice?~"_

_"SANS.." His eye sockets opened slowly._  
_"eh? what's up bro- hhgg!" Vines pinned his arms down to the wooden stand._  
_"Heyy, Smiley trashbag~ You look a bit rattled~ What's wrong? You look like you've seen a ghost~"_  
_"SANS, HELP!"_  
_"papyrus-" Vines wrapped around his throat. He trashed, his skull throbbing. "no!" Sans choked out. "please, dont hurt him,"_  
_"We've resulted to begging now?~ Oh, joy~ Let's see if you can save your brother this time!~"_

  
_"please," Sans gasped. "don't make me," His right eye's vision was entirely blocked. Sans whole body shook with fear._  
_"Ohh look~ Not so strong now, are you~ Ohh look!~ You're even trembling~ Let's watch your face contort in agony and sorrow as you kill everyone you know!~" His felt his body being forced to move._  
_"no-"_  
_"It's always so easy possessing skeletons, you know?~ They're really such numbskulls!~ Ahahaha!~"_  
_"stop it," He pleaded as he found himself advancing on Undyne and Papyrus practicing in the snow. "run!" He yelled, trying to resist._  
_"BROTHER- WHAT-"_  
_"What the hell?!"_  
_"run- you can't beat me,"_  
_"Smiley trashbag is right~ He has more power than you two combined~" Vines trapped Undyne and Papyrus, forcing them to their knees in the snow. Spears materialized._  
_"Sans! I don't want to hit you!"_  
_"Oh, you should not~ He only has 1 HP~ And I'm not as good as dodging as he is~"_  
_Bones formed around the two, attacking the helpless figures. "stop!"_  
_"The fun is only beginning~" Flowey giggled as Papyrus cried out in pain._  
_"no!" Sans felt his willpower draining away as he was forced to watch himself kill his friends._

Sans eyes snapped open. His skull was throbbing, and his magic felt burned out.  
"SANS, YOU ARE AWAKE." Papyrus said, touching his shoulder.  
"What the hell was that stunt you pulled?!" Undyne growled. "Frisk almost got hurt! You could have killed them."  
_'Sans! I don't want to hit you!'_  
"SANS?! CAN YOU HEAR ME?"  
_'BROTHER, PLEASE, WHAT ARE YOU DOING?'_  
_'Sans! Stop!'_  
'SANS- THIS HURTS-'  
'Sans!'  
'SANS'

_sanssanssanssanssanssanssans!_

"STOP IT!" Sans yelled, louder than he ever had before. "please, please please stop. just stop. get away get away get away-"  
"What the hell?! Snap outta it-"  
Sans lashed out in a blind fury and panic, shoving her away.  
"UNDYNE-"  
"Sans! I swear to god get a fucking grip!" Undyne yelled. "PAPYRUS. GET TORIEL IN HERE." Undyne growled.  
Papyrus ran out of his room, calling Toriel's name.  
"Sans. Sans, it's Undyne."  
"u..undyne.. run.. keep pap..papyrus.. safe." He choked out, lashing out at things that weren't there. He summoned a blaster with a shaky arm.  
"SANS!" Undyne barked, lunging at him, managing to get his arms to his sides. "PAPYRUS, TORIEL, HELP ME OUT!" Undyne screamed, struggling against Sans, who was lashing out.  
A bone grazed her shoulder, and she yelped in pain, feeling her HP drop to halfway. "Sans! Stop it!"  
"BROTHER, DO NOT ATTACK US!"  
_'SANS, PLEASE, WHY ARE YOU HURTING US?!'_  
' _Sans! Stop_!'  
"Sans!"  
Toriel's voice cut through the screams in his head. "Sans! Please calm down!" Toriel rushed over despite Undyne and Papyrus' warnings. "Sans, can you hear me..?"

His breathing steadied, his left eye flickering out to match the hollowed black of the other. "haha.. hahahahaha.. hahahahahaha!" He laughed, covering his head.

In the middle of Papyrus' room, Sans laughed hysterically, the worried attempts of his friends in were in vain.

"hahaha.."

**Notes for the Chapter:**

> I have a new fic in mind :0   
> Will be posted in the notes at the end of the next chapter, so please tell me what you think!   
> Feedback is much appreciated on this one too! <3


	4. (ANNOUNCEMENT)

**Summary for the Chapter:**

> READ THE CHAPTER PLEASE,  
> SOME REALLY IMPORTANT ANNOUNCEMENTS AND UPDATES.

hey.

i know i haven't been updating this at all in the past few months.

this fic is on a hiatus, could be permanent, we'll see.

but if i do continue it:

major updates*

updates every week*

this is only a possibility though

however, a likely chance of a new fanfic coming c:

thanks for sticking with this fic, and hopefully i'll be able to update more in the summer when school is over. 

again, thanks!

-sans


End file.
